Heavy duty electrical switching means



Jul 17, 1962 N- P. BA ETAL- 3,045,130

HEAVY DUTY ELECTRICAL SWITCHING MEANS Filed Feb. 18, 1959 4 Sheets-Sheet 1 i l l July 17, 1962 BASHOR ETAL 3,045,130

HEAVY DUTY ELECTRICAL SWITCHING MEANS Filed Feb. 18, 1959 4 Sheets-Sheet 2 July 17, 1962 BASHOR ETAL 3,045,130

HEAVY DUTY ELECTRICAL SWITCHING MEANS Filed Feb. 18, 1959 4 Sheets-Sheet 3 IN VENTORS July 17, 1962 N. P. B'ASHOR \ETAL HEAVY DUTY ELECTRICAL SWITCHING MEANS 4 sham-sheet 4 Filed Feb. 18, 1959 5 R O T. m V m United States Patent 3,045,130 HEAVY DUTY ELEQTRICAL SWITCHING MEANS Nelson P. Bashor and Werner Raap, Rockford, 111., as-

signors to W. F. and John Barnes Company, Rockford, 111., a corporation of Illinois Filed Feb. 18, 1959, Ser. No. 794,191 Claims. (Cl. 307-115) This invention relates generally to electrical switching means and more particularly to electrical switching means for heavy duty uses.

In a process mechanism, the ability to perform any one of or a combination of a number of selected operations at a given work station can be shown to create a distinct economic advantage. By such an arrangement, both equipment costs and floor space requirements can be reduced substantially. However, in order to realize these advantages, there must be devised some means of selectively applying power to a specified unit in the group of machines carried on the customarily rotatable indexing platform.

Since the machining units ordinarily considered for such a multiple-operation work station draw considerable power, in the neighborhood of 30 kilowatts at 440 volts, slip ring arrangements are inappropriate because of the difliculty in protecting them from dirt and damage and because of the complicated, space consuming arrangements which might become necessary. Likewise, parallel electrical connection of the several machines is disadvantageous because the machines operating other than at the workpiece would present a definite safety hazard. As a result of these problems, heavy duty, multiple-operation work stations have not heretofore been common.

Therefore, an important object of the present invention is to provide electrical switching means which are particularly useful in heavy duty applications.

Another object of the present invention is to provide electrical switching means which avoid the possibility of arcing. W

Yet another object of the invention is to provide electrical switching means which require no flexing of power cables.

Still another object of the invention is to provide heavy duty electrical switching means which are simple in both construction and operation.

A further object of the invention is to provide heavy duty electrical switching means through which power is conducted only when the working units are required to perform their operations.

A still further object of the invention is to provide electrical switching means which are interlocked with the working unit. 7

Additional objects and features of the invention pertain to the particular structure and arrangements whereby the above objects are attained.

The structure in accordance with the invention includes a stationary contact assembly connected to a source of power, a movable contact assembly associated with an electric machine, a retractable bridge for making electrical contact between the stationary and the movable contact assemblies, and suitable control elements.

The invention, both to its structure and mode of operation, will be better understood by reference to the following disclosure and drawings forming a part thereof, wherein:

FIG. 1 is a schematic side view of a multiple-operation work station utilizing electrical switching means in accordance with the present invention;

FIG. 2 is a fragmentary plan view partially in invisible outline of the showing of FIG. 1;

FIG. 3 is an enlarged fragmentary side view in partial 3,045,130 Patented July 17, 1962 section showing details of the electrical switching means;

FIG. 4 is a partial view in perspective of contact elements as used in the electrical switching means in accordance with the invention;

FIG. 5 is a sectional view showing details of the contact connections;

FIG. 6 is a sectional plan view showing alignment of the contacts; and

FIG. 7 is a schematic wiring diagram for use vw'th the electrical switching means shown in FIG. 1.

Referring now in detail to the drawings and specifically to FIG. 1, the multiple-operation work station comprises a base 10 carrying an indexing platform 12 to which is mounted a number of machining units 14. Each of the machining units 14 conveniently includes a drive motor 16, power transmitting means 18 and tools 20.

In a preferred embodiment, the mounting base 10 is stationary and the workpiece 22 which is fastened to slide 24 by fixture 26 is hydraulically moved into engagement with the tools 20. As the machining operations are completed and the workpiece 22 is retracted out of engagement with tools 20, platform 12 may be rotated, as by a hydraulically operated rack and pinion arrangement, in order to properly index the next desired machining unit. It is recognized that platform 12 may be equally as well arranged to locate the machining units by an oscillating motion.

The power necessary for operating the drive motors 16 is transmitted through a power conduit contained within the stationary head 28. Affixed to the head 28 and in electrical contact with the power conduit carried therein is a stationary contact block or assembly 30. Through the retractable contact bridge 32, power is conducted from the block 34 to movable, load contact blocks or assemblies 34 which communicate with the drive motors 16 and other operating electrical devices included in the several machining units 14. Bridge 32 may advantageously be operated by means of an air cylinder 36.

Since the structure and operation of the machining units and the other elements directly related to fashioning the workpiece do not pertain to the present invention, they will be considered here in no further detail. Turning therefore to FIG. 3, contact blocks 34 are shown assembled on housings 40 which, in turn are afiixed to a plate 42. Plate 42 is arranged to be rigidly fastened to the platform 12, as through support members 44 afiixed to the machining units 14, so as to move in correspondence therewith.

Plate 42 is further fastened to a central bearing post 46 as by means of brackets 48 and 50 and bolts 52 and 54. As shown, post 46 is provided with an axial hole 56 adapted to receive the shaft 58 and to be freely rotatable thereabout. Shaft 58 may be ailixed securely to the stationary head 28 in any suitable manner.

Since a contact block 34 is advantageously provided to operate each of the machining units 14, plate 42 is adapted to carry a number of these contact blocks, such as block 34a. Conveniently, each of these contact blocks is mounted on an individual housing, such as 40a. To prevent dust and other foreign matter from accumulating on the exposed surface of contact blocks 30 and 34, these blocks may bedisposed vertically, as shown.

In order to implement the operation of retractable bridge 32 by air cylinder 36, there is provided an arm 60 attached to the piston 62 of air cylinder 36, cylinder 36 being mounted to head 28 by a clevis arrangement 61. Arm 60 is connected to an offset arm 64 by means of pivot pin 66. Thus arranged, arm 64 is enabled of being operated about the shaft 68 to which it is rotatably mounted, shaft 68 being secured to the stationary head 28 as by means of bracket 70. 1

Bridge 32 may be afiixed to the arm 64 in some suit able manner, as by means of insulating assembly 72; and as best shown in FIG. 5, bridge 32 may advantageously be comprised of a bar 74 to which is attached a pair of contacts 76. Bar 74 and the contacts 76 are desirably fashioned from highly conductive material, it having proved useful in one particular embodiment to make bar 74 from copper and the contacts 76 from silver. Since it may prove advantageous to direct bridge 32 to close a number of separate circuits, an appropriate number of contact carrying bars 74 electrically, insulated from one another, may conveniently be included in the bridge 32, accordingly as best shown in FIG. 4.

Returning to FIG. 5, the stationary contact block 30 has a conductive bar 80 carrying a contact 82 afiixed to the insulating element 84 as by means of nut-and-bolt arrangement 86. Within the housing 88, nut-and-bolt arrangement 86 makes contact with power applying means including an electrical conductor 99, thereby extending electrical connection from the power conduit contained within the head 28 to the contact 82.

In like manner, block 34 includes a conductive bar 92 which carries a contact 94 and which is afixed to the insulating element 96 by means of a nut-and-bolt arrangement 98, the nut-and-bolt arrangement 98 completing electrical contact to. the conductor 100. Insulating elements 84 and 96 may conveniently be provided by appro priately milling a piece of some suitable material such as a fabric-reinforced phenolic plastic.

So as to facilitate making the various combination of connections which may be required by the several machining units 14, contact blocks 34 are adapted to receive the conductive bars 92 in a number of different locations, as best shown in FIG. 4. The number of potential locations for the bars 92 is not significant except that the total number of locations should correspond with the maximum number of connections necessary for any one of the machining units.

Whereas the movable block 34 does not necessarily have a conductive bar 92 in every possible position, both stationary block 30 and bridge 32 are arranged to make contact at every possible position on the block 34, this being done in order to insure completion of all the necessary circuits for the operation of each of the machining units.

According to an important feature of the invention, full power is applied to the contact block 30 only during those periods when it is desired to have a machining unit perform Work. Implementation of this feature may be achieved in a number of suitable ways, for example, by applying control to the circuit as by means of positional sensors or limit switches.

For example, when a machining operation is completed, such completion may be sensed by a limit switch 110 arranged to be operated by means of slide 24, as best shown in FIG. 1. Under the initiation of limit switch 110, heavy current through block 30 may be cutoif and slide 24 may be directed to withdraw the workpiece 22. When this withdrawal is achieved, a second limit switch 112 may be operated accordingly to cause air cylinder 36 to retract bridge 32.

When bridge 32 is completely retracted, a third limit switch 114, shown in FIG. 3, may be operated to initiate indexing of the platform 12. A fourth limit switch arrangement 116 may be adapted to indicate the proper position of the platform 12, signaling air cylinder 36 accordingly so as to operate bridge 32. Since a number of the machining units 14 are ordinarily provided, it is advantageous to arrange limit switch arrangement 116 to sense which of the machining units has been indexed into alignment with the workpiece 22. One such arrangement which has proved satisfactory includes a number of switch arms 120 engageable with stops 122 affixed to some part of the structure carrying the movable blocks 34, such as the housings 40. For example, by employing three arms 120 appropriately interconnected, it becomes apparent that a combination of the stops 122 may be made to provide an indication of which machining unit of the six shown in the drawings is indexed into position with the workpiece.

Furthermore, it is advantageous to have the contacts 76 of bridge 32 firmly seated before full power is applied thereto. This feature may be achieved by providing a sensing circuit comprising a special set of contacts in the block 30 and the bridge 32, which contacts close after and open before the main contacts, whereby application of full power to the main contacts may be directed.

Obviously, indexing units 14 also indexes one of the contact blocks 34 into alignment with the stationary block 30. So that small misalignments of the respective contact blocks need not frustrate proper electrical connection, the contacts 76, 82, and 94 are arranged to have sufficient width to allow a suitable amount of play in the alignment of the contact blocks. As shown in FIG. 6, misalignment by the distance shown as 130 does not prevent firm contact between the contacts 76 and the contacts 82.

With reference to FIG. 7, making electrical contact between block 30 and block 34a energizes a circuit to the machining unit 14a, including drive motor 16a and other desirable electrically operated devices, such as thermal overload a. In like manner, an indexing of platform 12 so as to align block 30 with block 34b, 34c, 34d, 34c, or 34 will make possible completion of an electrical circuit to the corresponding machining units 1411, 14c, 14a, 14a, and 14f respectively.

In one specific embodiment of the invention, it has proved desirable to space the contact block 34a away from its corresponding machining unit 14a, accordingly as shown in FIG. 7. By this arrangement, the stationary contact block 30 and the related electrical connections are isolated from physical damage as might be incurred from flying chips, coolant and lubricants which may be associated with the functioning of the machining unit.

Operation of the electrical switching means of the present invention will be apparent from the above descriptions.

The specific example herein shown and described is illustrative only. Various changes in structure will no doubt occur to those skilled in the art. For example, it may become advisable to shroud the contact bridge to further protect the electrical contacts. Therefore, such changes are to be understood as forming a part of this invention insofar as they fall within the spirit and scope of the appended claims.

The invention is claimed as follows:

1. Apparatus for making electrical connections at a multiple-operation machining station comprising: a stationary contact assembly connectedto a source of power; a plurality of rotatable contact assemblies individually alignable with respect to said stationary contact assembly, each of said rotatable assemblies being electrically connected to and arcuately spaced apart from a correspondingly movable, electric machine; a retractable contact bridge adapted to provide selected electric contact between said stationary assembly and said rotatable assembly aligned therewith; bridge operate means for urging said bridge into and out of contact with said stationary assembly and said rotatable assembly aligned therewith; first sensor means responsive to the alignment of said stationary assembly and said rotatable assemblies; second sensor means responsive to the condition of electrical contact between said stationary assembly and said rotatable assemblies; and power applying means disposed between said stationary assembly and said source of power for selectively applying power to said stationary assembly in accordance with signals received from said first and said second sensor means.

2. Apparatus for making electrical connections at a multiple-operation machining station comprising: a stationary contact assembly connected to a source of power;

a plurality of rotatable contact assemblies individually alignable with respect to said stationary contact assembly, each of said rotatable assemblies being electrically connected to and arcuately spaced apart from a correspondingly movable, electric machine; a retractable contact bridge adapted to provide selected electric contact between said stationary assembly and said rotatable assemblies; bridge operate means for urging said bridge into and out of contact with said stationary assembly and said rotatable assemblies; first sensor means responsive to the alignment of said stationary assembly and said rotatable assemblies; second sensor means responsive to the condition of electrical contact between said stationary assembly and said rotatable assemblies; and power applying means disposed between said stationary assembly and said source of power for selectively applying power to said stationary assembly in accordance with signals received from said first and said second sensor means, whereby power is directed to said electric machines only during desired periods.

3. Apparatus for making electrical connections at a multiple-operation machining station comprising: a stationary contact assembly including a plurality of silvertipped contacts connected to a source of power; a plurality of rotatable contact assemblies including pluralities of silver-tipped contacts individually alignable with respect to the silver-tipped contacts of said stationary contact assembly, each of said rotatable assemblies being electrically connected to and arcuately spaced apart from a correspondingly movable, electric machine; a retractable contact bridge including a plurality of silver-tipped contacts adapted to provide selected electrical contact between said stationary assembly and said rotatable assemblies; bridge operate means for urging said bridge into and out of contact with said stationary assembly and said rotatable assemblies; first sensor means responsive to the alignment of said stationary assembly and said rotatable assemblies; second sensor means responsive to the condition of electrical contact between said stationary assembly and said rotatable assemblies; and power applying means disposed between said stationary assembly and said source of power for selectively applying power to said stationary assembly in accordance with signals received from said first and said second sensor means whereby power is directed to said electric machines only during desired periods.

4. Apparatus for making electrical connections in a multiple-operation machining station which incorporates motive means drawing appreciable quantities of electrical power, said apparatus comprising: a stationary, heavy duty contact assembly connected to a source of power for said motive means; a plurality of heavy duty load contact assemblies mounted on a movable platform, each of said load contact assemblies being electrically connected to and spaced apart from a said motive means mounted on said platform, said load contact assemblies being individually alignable with said stationary contact assembly by movement of said platform; and a reciprocable, heavy duty contact bridge providing selected electric contact between said stationary contact assembly and the load contact assembly aligned therewith.

5. Apparatus according to claim 4 and further comprising bridge operate means for urging'said contact bridge into and out of electrical contact with said stationary contact assembly and the load contact assembly aligned therewith.

References Cited in the file of this patent UNITED STATES PATENTS 1,973,369 Burgess Sept. 11, 1934 2,039,581 Brown May 5, 1936 2,163,069 Stringer June 20, 1939 2,511,821 Bullard June 13, 1950 

